The Inventor believes that the cable television industry is at the doorstep of a major transformation from acting primarily as a supplier of entertainment, as it does presently, to acting as a supplier of communication services generally. These communication services will be two-way, and interactive.
Such two-way communications are expected to include audio and video telephony, ISDN-like digital services, and video servers. (Video servers store large amounts of video data, such as movies, at a central location, in a form which is compressed or encrypted, or both. The data is stored in a fast memory, such as solid-state RAM. To a user, the video server appears as a remotely located video tape machine. The user can order retrieval of stored data, such as a movie, causing the video server to transmit the data to the user.)
An interface will be necessary to allow each subscriber to transmit information to a local cable service provider. It is desirable that these interfaces be low in cost. The invention addresses one aspect of a cost-effective design for the interface.
The Inventor believes that all feasible interfaces will require a modulator to place information onto a radio frequency (RF) carrier for upstream conveyance, to the cable service provider. The Inventor proposes (1) a Surface Acoustic Wave (SAW) filter, for defining the RF modulator's bandwidth, and (2) a mixer for converting the upstream signal to another frequency. The conversion allows the frequency, or channel, used by the subscriber to be changed, and changed dynamically, if required.